This invention relates generally to improvements in intraocular lenses of the type designed for implantation into the eye as a replacement for a surgically removed natural lens. More specifically, this invention relates to an improved intraocular lens including support or haptic means adapted for a high degree of visibility during implantation surgery and in the course of postsurgical examination. The improved lens of the present invention is especially suited for posterior chamber implantation.
Intraocular lenses in general are well-known for implantation into the eye as a replacement for a natural crystalline lens which has been removed surgically due to a cataract condition, injury, or the like. Such intraocular lenses are typically constructed from a transparent lens body of a selected, relatively inert and optical grade plastic material, such as polymethylmethacrylate (PMMA), having a generally disk-shaped configuration providing optical characteristics approximating a natural lens. Resilient support loops or haptics are normally provided to project outwardly from the periphery of the lens body for supporting and centering the lens body with respect to adjacent delicate eye tissue. In accordance with some intraocular lens configurations, the lens body and support loops are designed for seating in the so-called anterior chamber of the eye in front of the iris and pupil, whereas other lens designs are intended for implantation within the so-called posterior chamber behind the iris and pupil.
In accordance with recent trends in ophthalmic surgery, posterior chamber lens implantation is preferred by many surgeons largely because the lens prosthesis is positioned within the eye at or near the original position of the natural lens. Such posterior chamber implantation of an intraocular lens commonly follows so-called extracapsular extraction wherein a central anterior wall region of a transparent capsular bag or membrane containing the natural lens is surgically removed to accommodate natural lens removal, while leaving the remainder of the capsular bag intact. The intraocular lens implant is inserted through the pupil margin into the posterior chamber, desirably with the support loops seated within the periphery of the capsular bag.
Posterior implantation of an intraocular lens including the support loops constitutes a relatively difficult surgical procedure. More specifically, significant lens manipulation is required in close proximity with delicate eye tissues to pass the lens through a dilated pupil and to seat the lens in proper orientation behind the iris. Restricted visibility of the lens and/or the support loops contributes significantly to the complexity of the surgical procedure. That is, the support loops often have a relatively narrow profile which combines with visibility restrictions to make it difficult or impossible for the surgeon to visually confirm proper placement of the support loops.
Postsurgically, in some cases, problems can arise with respect to lens movement within the posterior chamber. More particularly, the intraocular lens can shift to a tilted or otherwise decentered position, resulting in visual impairment. Unfortunately, such problems are often difficult to diagnose, as a result of difficulty in seeing the precise position of the haptic support loops within the posterior chamber.
There exists, therefore, a significant need for an improved intraocular lens of the type designed particularly for posterior chamber implantation, wherein the lens includes means for facilitating and/or enhancing visibility of the haptic support loops during surgical implantation and postsurgical examination. The present invention fulfills these needs and provides further related advantages.